fix(link): promisify detach, properly send closed flag in frame

lib/link.js

@@ -1,6 +1,7 @@
 'use strict';
 
 var EventEmitter = require('events').EventEmitter,
+    Promise = require('bluebird'),
     util = require('util'),
 
     StateMachine = require('stately.js'),
@@ -93,8 +94,22 @@ Link.prototype.attach = function() {
 };
 
 Link.prototype.detach = function() {
+  var self = this;
+  var detachPromise = new Promise(function(resolve, reject) {
+    self.once(Link.Detached, function(info) {
+      if (!!info.error) return reject(info.error);
+      if (!info.closed) return reject('link not closed');
+      resolve();
+    });
+
+    self.once(Link.ErrorReceived, function(err) {
+      reject(err);
+    });
+  });
+
   this.linkSM.sendDetach();
   this._sendDetach();
+  return detachPromise;
 };
 
 Link.prototype.isSender = function() { return this.role === constants.linkRole.sender; };
@@ -218,6 +233,7 @@ Link.prototype._detachReceived = function(frame) {
 Link.prototype._sendDetach = function() {
   var detachFrame = new DetachFrame(this.policy.options);
   detachFrame.channel = this.session.channel;
+  detachFrame.closed = true;
   this.session.connection.sendFrame(detachFrame);
 };